An optoelectronic assembly may include, for example, one, two, or more light-emitting diode elements. The light-emitting diode elements can be, for example, light-emitting diodes (LEDs) and/or organic light-emitting diodes (OLEDs) or parts or segments of light-emitting diodes (LEDs) or organic light-emitting diodes (OLEDs), respectively.
In spite of complex quality controls of light-emitting diode elements, it is not possible to completely preclude the spontaneous failure of the light-emitting diode elements in use. For example, in the case of an OLED, a typical fault picture for a spontaneous failure is a short-circuit (short) between the electrodes of the corresponding light-emitting diode element. A short-circuit of the electrodes of the light-emitting diode element intrinsically short-circuits or discharges the parasitic capacitance of the light-emitting diode element. Such a short-circuit typically has a small area. Therefore, a majority of the total current is concentrated in the small-area short-circuit point. The current density is therefore significantly superelevated in the short-circuit point, whereby this short-circuit point can heat up strongly depending on its area extension. This can result in fusing of the electrodes, dark spots in the light image of the OLED, a completely dark OLED, and/or a point which becomes hot on the OLED.
To avoid a potential hazard due to this overheating (hazard of combustion, fire, bursting, etc.), such a short-circuit should be recognized by driver electronics of the optoelectronic assembly and a suitable protective reaction should be initiated (shutdown of the OLED or the optoelectronic assembly, redirection of the supply current around the short-circuited OLED, output of a warning signal, etc.). For example, in the automotive field, it is required that defective OLEDs or LEDs, for example, in taillights, are electronically recognized and reported at least to the vehicle electrical system.
A routine interconnection of light-emitting diode elements, for example, OLEDs, of an optoelectronic assembly in use is, for technical reasons and reasons of cost, the series circuit of the light-emitting diode elements. For example, multiple light-emitting diode elements in a light-emitting diode can be connected in series and/or multiple light-emitting diodes can be connected in series. For many uses, for example, in the automotive field or in the field of general illumination, therefore, multiple light-emitting diode elements are electrically connected in series. If individual defective light-emitting diode elements in a series circuit are intended to be recognized using simple methods, this represents a special challenge.
Methods for ascertaining short-circuits of individual OLEDs are known from US 2011 204 792 A1, WO 2010 060 458 A1, and WO 2012 004 720 A2, in which an overvoltage or undervoltage at the corresponding OLED is used as a criterion for a defect. The recognition of the short-circuit is reacted to with a redirection of the activation current (bypassing) and/or with a fault signal generation.
In the field of general illumination, it is typical that flexible control devices have a variable output voltage range. A variable number of light-emitting diode elements can thus be connected to the control devices.